Percussion tool



Aug. 7, 1934. E. w. ROBERTS PERCUSS ION TOOL 2 Sheets-Sheet 1 Filed Nov.23.. 1951 E. W. ROBERTS PERCUSSION TOOL Aug. 7, 1934.

2 Sheets-Sheet 2 Filed Nov. 23, 1951 Patented Aug. 7, 1934 UNITED STATESPATENT; QFFHQE i I 1,969,153 I V i h i V PERCUSSION T0 OL Edmund W.Roberts, Cincinnati, Ohio, assignor to Robert D. OConnell and Joseph R.Sweeney, Cincinnati, Ohio, partners doing business as OConnell & SweeneyApplication November 23, 1931, Serial No. 576,839

6 Claims.

My invention relates to that type of percussion tool or hammer in whicha piston or plunger reciprocates axially in a cylinder, and strikes the7 end of a drill bit, chiseLtamper or other tool, at

the end of its outward stroke; the plunger functioning as the piston ofan explosion engine, and the blow being imparted by the force of anexplosion efiected upon the piston.

The internal combustion or explosion engine exemplified is of thetwo-cycle type, in which an explosion occurs at the beginning of eachoutward stroke of the piston.

It is the object of my invention toprovide a new and improved percussiontool of simple character and rugged construction and having few partscompactly assembled; further, to provide novel means for imparting theoutward stroke of the piston to the tool; and, further, to provide novelmeans for imparting forceful impact upon the tool.

it is the object of my invention, further, to provide novel means foractuating a ily-wheel by means of a piston and employing the inertia ofmotion of the fly-wheel for returning the piston during its compressionstroke and freeing the fly-wheel connection from the piston atapproximately the moment of actuation of the tool for imparting aforceful working stroke to the tool.

It is the object of my invention, further, to provide a novelarrangement of jacket space for the cylinder of an explosion engine, 'afiy-wheel, a magneto and a fan, the fan having communication with saidjacket spacewhich is open to the 7 outside air, and so constructed andarranged in novel manner as to draw the air over the mag- Fig. 1 is asectional elevation through th axis of the piston and the cylinder takenalong the line 11 of Fig. 2. Fig. 2 is a sectional elevation taken alongthe line 2-2 of Fig. 1, with the exception that about two-thirds of thepiston is not in section, and thecrankpin is shown in less advancedposition and as if out off close to the crank arm.

Fig. 3 is an end view as seen from the left of Figs. 1 and 2, with thehandles or grips removed.

'Fig. 4 is a sectional elevation of t e flywheel casing taken along. theline 44 of'Fig. the flywheel not in section. V

Fig. 5 is a diagrammatic view with the anvil block omitted, it beingassumed that the piston acts directly onthe tool-bit, and showing thepi's-' ton, crank, roller and tool-bit in their relations at the end ofthe compression stroke.

Fig. 6 is a similar view'of the parts, with the crank moved through' anangle of forty-five degree's.

Fig. 7 is a similar view of the parts with the piston in its workingstroke, and showing the outer end of the pistonadvanced beyond thebroken line, which represents the limit ofworking stroke q of a similarpiston coupled journalwise with; the crank. i I

Fig. 8 is a similar view of the parts, showing the piston at the end ofits power stroke.

Fig. 9 is a similar View of the parts, showing their relations at thebeginning of the return movement of the crank; and,

Fig. 10 is a similar'viewof theparts, showing the crank as having madean' additionaloneeighth revolution, prior to the parts againassuming therelations shown in Fig. 5,

In the drawings, the cylinder is indicated gen erally by the numeral 11.The cylinder has an outer or jacket wall 12, providing an annular spaceor jacket 13 between the cylinder and'the jacket wall. At'intervals inthe jacket space 13 are ribs 14, integral with thecylinder and'thejacketwall, providing longitudinal'air spaces 13' comprising thatportion of the jacket space contiguous to the left-hand end of thecylinder.

Bolted to the side of the cylinder uppermost in Fig. I isthe by-passplate or cover l5, providing a semi-annular space 16 correspondin tothebypass or transfer port of the average two-cycle engine. Bolted to the'side' of the by-pass plate; and registering'with the opening 17providedinthe plate, is the mixing valve 18. The tank 19 bolted to plate15 provides fuel storage, and'is connected with the gas valve ofthemixing valve by a tube not shown in the figures.

Within the cylinder 11, and adapted to reciprocate axially therein, isthe piston 20. The piston is provided with a longitudinal groove 21, in

1 with which is a guide roller 22, mounted on the threaded pin 23. Thepin projects through the q, by-pass plate 15, and is threaded in thewall of cylinder 11. This guide roller orother suitable guiding means-isadvisable to prevent the piston from turning on its axis.

Mountedon the side of the cylinder 11, and

held thereto by means of bolts 25,is' the side 1110' plate 24. In theside plate is journalled the crankshaft 26 within the ball bearings 27.The crankshaft comprises the crank arm 28 and the crankpin 29. Thecrankpin includes the roller 30 mounted on bearing rollers 31 on therigid part of the crank pin.

In that side of piston 20 nearestthe'side'plate 24 is provided a groove32'of which the lower portion 32 is a running fit to roller 30. Theupper portion is cut away, at the side nearest the cylinder head 53, atan angle of approximately The side of the piston is further cutaway toprovide the extensions 33 of groove 32 to clear crank arm 28.

The right-hand end of the piston is provided with a cup-shaped opening20" to receive the extension 34 of the anvil block 34. The anvil blockexemplified is shown-as a: supplemental or auxiliary piston providedwith packing. rings for making the outer end of the cylinder airtightagainst leakage from the pre-compression chamber which is in thecylinder between the anvil block-34 andthepiston 20. A similar opening34 is provided. in the anvil blockto receive the end of the tool bit36.. The extreme right hand end of the. anvil' block is provided. withanenlargementl3 5- registering with -a' correspondingly enlarged. bore35 in the end. of cylinder 11.. The. piston is arranged to strike theanvil block, which transmits the impact to the tool-bit.

Lower cylinder head: 37 is yieldingly attached to the cylinder throughthemedium or. the springs 38,.the bolts: 39,.and'the hook nuts at Head37 isprovided. with an opening suitable for the re-- ceptien. of-Qth-eaorta 36. Surrounding tool bit 36, and held loosely in one of the hooknuts 40, is. a tool-retaining link- 41; of. a type. frequently employedon air hammers to retain the tool bit when the hammer is lifted,

Mounted onQthecrankshaft 26, and. fixed thereto, is the flywheel 42.Within the rim of the flywheel is mounted the ring-shaped magnet 43,which is one of the constituent parts of the flywheel magneto. In Fig. 4are indicated the relative positions of the-magneto coil 44, and thecircuit' breaker 45. In thisv figure they are. shown asdetached from theplate 46 (Fig.1) to'wh-ich they are fastened. Since the functioningflof' this type of magneto iswell known in the art, furtherdescription thereof isunnecessary.

Integral with the-flywheel arethe fan blades 47,. which serve to drawair through the cylinder jacket- 13, and through the compartmentsurrounding the magneto, and to discharge the air 1 tov the atmosphere.Inaddition tothe cooling air,

exhaust gases.- discharged from the cylinder through exhaust port X,.enter the fan to be dis-- charged therefrom.

7 To guard againstover-heating the magnet 43 and: thereby demagnetizingit,v the magnetis mounted within the. flywheel rim with its outerperiphery incontact with ribs 4?? extended f-rom the blades-47. are.provided air spacesbetween the ribs, theinside of thefiywheel-rim, andthe outer surface'of the magnet; through which air may be drawn inaddition to -that circulating through the- -magneto compartment,Further- I more, less heat will pass by conduction from-the flywheel:rim: to the-magnetthrough the ribs than ifthemagnet were: in contactwith the entire inner surface-of the rim.

Partially surrounding the flywheel 42' is an extension 24 of theside'plate 24 comprising a; hood to deflect the gases: leaving the fan.from striking" the operater in the face. The. lower (Fig. 4) is open.Across the opening provided in extension 24 are guard bars 48 and 49.

In the wall of cylinder 11 are provided the ports 0, I and X. Port Cprovides for ingress of the mixture from the mixing valve 18 into thespace: providedibetween the piston 20 and the anvil block 34. It alsoprovides for egress of the mixture from the cylinder to the by-pass 16.Port I provides apassage for the mixture to enter the cylinder from thebypass. Port X provides a: passage way for the egress of the exhaustgases from the cylinder tothe flywheel fan, whence they are"dischargedtothe atmosphere. The defle'ct'or 20", integral with piston 20, bars thenew mixture. entering port I from passing directly across the end of thepiston to port X, and deflects the mixture toward the head of thecylinder.

Bolted to plate 24 is the cover plate 50 provided with an opening 51surrounding the crankshaft nut 26', and providing a space between thenut and the. plate for the insertion of a suitable starting crank. Thesame space further pro vides a passage way for air to enter the magnetocompartment, the entering airpassingthrough openings 52' provided in thewebof the flywheel.

Bolted to the left-handend of the-cylinder 11, is the cylinder head 53'in which is the spark plug54. Attached to head 53 are ears 55 providedwith internal. screw threads for the reception. of' the handles. 56.Covering the handles are the grips 57', preferably ofrubber fabric, aheavy steamhose. making a satisfactory grip.

In the operation of the invention, the machine is started in the samemanner as any small explosion engine. by spinning the flywheel with a.suitable starting crank. The sequence, of events of the cycle are thoseof any two-cycle explosion. engine in which the mixture first entersthe. crank-case to be discharged therefrom into the bypass with thedifference that the functions' of the enclosed crankcase are performedby the space provided between the end of piston. 20 and anvil block 34.Since the functioning of a twocycle. engine is wellknown to the art, nodetailed description will be given The adaptation. of the invention tothe requiren'ientsv of a. percussion tool is shown in thedirectly by theend-ct the piston 20 The rela tive positions of the piston and. the toolbit are shown tothe same scale in each of the. figures.

In Fig. 5, the roller 3 0 has thrust piston 20 to the limit of the.inner or compression stroke. It will be noted that the innerdead centerposition ot'the roller has-not been: reached, and that further rotationof. the crankshaft will. not drive the piston further to the left, owingto the conformation of groove: 32.

In: Fig.6 the crankshaft has turned through an angle of 45 after passingthe inner dead cen- 1 ter. The piston is shown. as it would follow theroller when impelled: by the. force of an explosion in the cylinder,with the slanting. side of the groove bearing against the roller.. Thecrankshaft isbeing: driven by the piston, storing up kinetic energy inthe flywheel; It should be noted that thepiston has made approximately ahalf of its normal stroke whil'e'the crankshaft has been making butone-fourth of the half revolution corresponding to the full stroke inone direction of the piston, the piston moving faster than the roller.in the axial direction of the piston.

In Fig.7, the crankshaft is shown as having made a quarter revolutioncorresponding to a half .stroke of the piston, while the piston has mademore than a normal 'full stroketo strike the end of the tool bit. Thebroken line near the right hand end of the piston indicates what wouldbee. normal full stroke, that is, the position of that end of the pistonhad it been reciprocated by the crankshaft with the roller bearingagainst the right-hand side of the groove.

It should .be noted that if the pistonwere re.- ciprocated by thecrankshaft through the medium of the roller in contact with theright-hand side of the cross groove in the piston, the piston would notcome into contact withithe end-of the tool bit, or strike the anvilblock 34 in the combination illustrated in Figs: 1 and 2. The axialdistance between the broken line near the righthandof the piston andthat shown by the solid line in Fig. '7 represents the over-run of thepiston at the instant of impact. i

In Fig. 8, the crankshaft has made another oneeighth revolution, and theroller is 135 past the inner dead center position. The impact of .thepiston under the impelling force of the explosion has driven the toolslightly to the right of the position it normally occupies, as indicatedin the previous figures, as shown by the greater distance between thedotted line and the end of the piston as compared with the intervalindicated in Fig. 7. The roller is now out of contact with both sides ofthe groove 32, and the axial movementof the piston is unrestrained bythe roller. This freedom of restraint permits the piston to followthrough and exert the full force of the explosive impulse upon the endof the tool bit, less only that small proportion of this force requiredto keep the. flywheel in movement and to compress the mixturein theright hand end of the cylinder.

In Fig. 9 the crankshaft is shownas having made slightly more than afull half turn and the piston has rebounded from the tool bit, to starton its return stroke. Itshould be noted that the right-hand side ofgroove 32 has not quite come into contact with roller 30. a

In Fig. 10 the crankshaft has made a oneieighth revolution past theouter dead center position of Fig. 9. The roller has entered the lowerhalf.32" of the groove 32, and the piston is now being impelled by'thecrankshaft from the energy stored in the flywheel to compress theexplosive mixture in the explosion chamber, at the left of the piston.This condition continues until-the relative positions-of the crankshaftand the piston are as in Fig. 5.

My improved device starts readily with the spark at the full advancerequired for best results at working speed, and throttle control andspark control may be omitted, thus materially simplifying the mechanism.

The apparatus has the peculiar faculty of operating more slowly when notcrowded to the work than when the operator thrusts downward on thehandles. For example, when the tool is lifted or when it is allowed torun by itself supported on a tamper, it will run at about 400 R. P. M.Crowded to the work it will speed up to .tont'o start-it on the .inwardstroke.

instant the piston strikes the tool-bit.

its normal working speedof 1100 R. P. M. or more. In explanation of thisit may be stated that in my improved device the return stroke of theme-:ton is-started by its rebound from the tool-bit. Furthermore, thestroke is slightly shorter when the 'tool' is crowded. When idling, theforce of the recoil is less, the distance through which the piston mustrebound is longer, and thecrankshaft has more work to do in picking upthe pie- Hence, more of the energy stored in the flywheel must beexpended to return the piston than when the rebound .is more vigorous,as 'when the tool is crowded. The speed of the tool may in consequencebe regulated by the pressure on the handles. r

In my improved device, the widenedportion of the cross-groove in thepiston provides for the detachment of the piston from the rotating partsat the moment of impact, so that the major porsaid cylinder, of a pistonaxially reciprocable in' said cylinder, the piston having a grooveprovided therein within the cylindrical projection-of the inner'face ofsaid cylinder .and intermediate of the ends of said piston, the grooveat a right angle to theaxis of the piston andin one'side thereof, saidtool-bit slidably mounted at said :other end of the cylinder,the pistonoperative to move the tool-bit; a crankshaft journalled on the cylinderand radial with relation to said piston, a flywheel on the crankshaft, acrankpin on the crankshaft, and a roller on the crankpin, the roller inthe groove, a portion of the groove being a substantiallyrunning fit-tothe roller, another portionof the groove being wider'than the diameterof the roller, the sides of said cylinder opposite the respective endsof said groove provided with recesses in which said roller isalternately received, and

the wider portion of the groove so conformed that thepiston may movefaster than the roller when impelled by an explosion in the cylinder,and that the piston is free of restraint by the roller at the 2.;1'napercussion tool, the combination of ;a cylindenan explosion chamber atone end of said cylinder, 2. tool-bit slidably mounted at the other endof said cylinder, a piston axially reciprocable in said cylinder, saidpiston having a groove solely'in one of its sides between its endswithin the. cylindrical projection of the inner face of said cylinderatsubstantial right angles to the axis of said piston and extending intosaid piston substantially to saidaxis, said piston operative to movesaid tool-bit, a crankshaft journaled on said cylinderradial withrelation to said axi i a crankon said'crankshaft' located in said grooveadjacent to said axis, and a flywheel on said crankshaft, the wall ofsaid groove toward said explosion chamber having a slanting portion atone of its ends slanting outwardly toward said explosion chamber forwidening said end of said groove and acting on said crank duringexplosion movement of said piston for rotating said crank- Mil shaft,said explosion movement being also the iimpelling stroke of said pistonfor impelling said tool-bit, the other end of the walls of said groovebeing substantially right-angular with relation to said axis, said crankhaving a substantially running fit with said other end of said walls for7 1 in line with said groove provided with recesses returning -.said.piston into said explosion :chamstant of impact 4 producing benthewalls of said widened end ofsaid-groove soconforni'edthat the pistonmaymove .faster in axial direction'than the crank during-such inone of itssides between its ends within the cylindrical projection of the innerface of said cylinder at substantial right angles to the "axis :ofsaidpiston and extending into said piston substantially to saidaxis, saidpiston operative to, move said tool-'b'it,a crankshaft journaled on saidcylinder radial with relation to said axis, a crankarm on saidcrankshaft, a crank on said i crankarm located in said grooveadjacent-to said axis, and :aflywheel on said crankshaft, the wall ofsaid groove toward said explosion chamber having a slanting portion atone ,Of its ends slanting outwardly'towa'rd isaid'explosion chamber tornidenin'g .saiden'd of said.- agrdove and acting on 'saidhcrank duringexplosionmovement o f saidpiston ffor rotating said crankshaft, "saidexplosion movement :ibeing also vthe impelling' stroke of said pistonfor impelling :sa'id tool-bit, said piston provided with a recess attheside of said widened end of groove, said 'cran-karmextendingintclsaid 'IEfiESSythG otherzrend otithe j walls of :said:groove'being' substantial-1y i-r'ightangular with relation'to saidaxis, said crank hav ing -:a substantially running ifit with said other=end o=f said walls for returning saidpiston into said explosionchamber; thewallsio-f said widened I end 'of said groove so contormedthat the piston may move faster in axial direction tlranthecrank duringsuch impeding stroke I of said piston, and saidpiston-be-ing tree of"restraint by said crankat the instant of impact producing the puttingstroke of thetool-hit.

-4. In :a percussion t col,.1the.comhinatioii of :a cylinder, anexplosion'chamber atone lend of said cylinder, .a tool-hitslidahlymountedaa-t the other end of saidcylinder, api-ston =ax-ia1ly'r-e-' lciproca ble in said cylinder, said piston having a groove solelyin oneof its sides between its ends within the cylindrical projection of theinner face of the cylinder at substantial right angles to the axis ofsaid piston and extending into said piston substantially to said axis,said piston operative to move said tool bit, a crankshaft journaled onsaid cylinder radial with'rel'ation to said axis, a crank on saidcrankshaft located in said groove adjacent to said axis, the sides ofsaid cylinder between the ends of said piston in which said crank movesbeyond the cylindrical projection momma wolf said, piston, anda flywheelon said crankshaft, the, wall :of :said .grooye toward said explosion ofsaid iwidened end of said groove soconformed that the piston may movefaster in axial-direc- .tionjzth an the crank duringsuch impellingstroke of saidipiston, and said piston being free of restraint :by saidcrank'aat the instant of impact producing the [cutting stroke ofthetoolebit.

5 In a percussion tool comprising an explosi'on engine; the "combinationoi -.a cylinder, a-piston reciprocable therein :andrarranged to operatea tool; a jacketewallsurrounding said cylinder, a

jacket-space provided between said jacket-wall and said icylin'deig'said .jacketespace having connection with the atmosphere, .3,crank-shaft for said piston journaled on said cylinderrat right anglesto the axis of said. piston, any-wheel fixed tosaid crank-shaft,said'fly-wheel locatedisolely .at one side of said "piston, saidfly-wheel provided with a fanaspace, an air-conduitbetween :saidjacket-space and said fan-space, fan-blades insaid fan-spacefixed tosaidfly-wheel andaa magneto incorporated in said fly-wheel at the same.side of said piston, and said ifanebla'des operative to draw airthrough ssaidvjacketespace and said conduit and'over saidmagneto.

6; In a percussion-tool comprising an explosive engine, the combinationof a cylinder, -.a piston reciprocabletherein and arrange'd'to operate atool, a jacket-wall surronndingrsaid cylinder, at jacket-space providedbetween said jacket-wall and said cylinder, said jacketspace havingconnection with the atmosphere,v a crank-.shaftior said pistonjournaled. on said cylindersati right angles to the. axis of saidpiston, a fiy-wheel fixed to said crank-shaft, a casing about said:flywheel, said casingland said fly-wheel .havinga fan-spacetherein,'said casing provided withan air outlet communicating with saidfan-space, an airv conduit between said jacket-space ,zanid vsaidfan-space, said fly-wheel and said casing with said fan-spacethereinlocated solely at one side of said piston,.fan'-blades in .saidfan-space fixed to said fiy-whee'l, and amagneto incorporated'in saidfly-wheel .at the same side of. said piston and located in said.vfan-space, and said Lfanblades operative to draw air through said.jaokotspace and through said air conduit over said magneto.

EDMUND ROBERTS.

